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In this study, we have examined the major platelet-derived CXC chemokines connective tissue-activating peptide III (CTAP-III), its truncation product neutrophil-activating peptide 2 (CXC chemokine ligand 7 (CXCL7)), as well as the structurally related platelet factor 4 (CXCL4) for their impact on neutrophil adhesion to and transmigration through unstimulated vascular endothelium. Using monolayers of cultured HUVEC, we found all three chemokines to promote neutrophil adhesion, while only CXCL7 induced transmigration. Induction of cell adhesion following exposure to CTAP-III, a molecule to date described to lack neutrophil-stimulating capacity, depended on proteolytical conversion of the inactive chemokine into CXCL7 by neutrophils. This was evident from experiments in which inhibition of the CTAP-III-processing protease and simultaneous blockade of the CXCL7 high affinity receptor CXCR-2 led to complete abrogation of CTAP-III-mediated neutrophil adhesion. CXCL4 at substimulatory dosages modulated CTAP-III- as well as CXCL7-induced adhesion. Although cell adhesion following exposure to CTAP-III was drastically reduced, CXCL7-mediated adhesion underwent significant enhancement. Transendothelial migration of neutrophils in response to CXCL7 or IL-8 (CXCL8) was subject to modulation by CTAP-III, but not CXCL4, as seen by drastic desensitization of the migratory response of neutrophils pre-exposed to CTAP-III, which was paralleled by selective down-modulation of CXCR-2. Altogether our results demonstrate that there exist multiple interactions between platelet-derived chemokines in the regulation of neutrophil adhesion and transendothelial migration.

Intracellular persistence of mycobacteria may result from an intricate balance between bacterial replication and signaling events leading to antimicrobial macrophage activities. Using human monocyte-derived macrophages, we investigated the relevance of mitogen-activated protein kinase activation for the growth control ofMycobacterium aviumisolates differing in their abilities to multiply intracellularly. The highly replicative smooth transparent morphotype ofM. aviumstrain 2151 induced significantly less p38 and extracellular signal-regulated kinases 1 and 2 (ERK1/2) phosphorylation than the smooth opaque morphotype of the same strain, which was gradually eliminated from macrophage cultures. Inhibition of the p38 pathway by highly specific inhibitors did not significantly affect mycobacterial replication within macrophages, regardless of the in vitro virulence of theM. aviumstrain. However, repression of the ERK1/2 pathway further enhanced intracellular growth of highly replicativeM. aviumstrains, although it did not increase survival of the poorly replicatingM. aviumisolate. Inhibition of the ERK1/2 pathway resulted in decreased tumor necrosis alpha (TNF-α) secretion irrespective of the virulence of theM. aviumisolate used for infection, revealing that TNF-α could have been only partially responsible for the control of intracellularM. aviumgrowth. In conclusion, ERK1/2- and TNF-α-independent pathways are sufficient to limit intramacrophage growth of less-virulentM. aviumstrains, but early ERK1/2 activation in infected macrophages is critically involved in controlling the growth of highly replicativeM. aviumstrains.

Human monocytes (Mo) consist of a major subset of Fcgamma-receptor I (CD64)-positive typical low accessory phagocytes, and a minor CD64(-) DC-like subset with high T cell-accessory and IFN-alpha-releasing activity. Both populations also differentially express CD16 (Fcgamma-receptor III). Double labeling with anti-CD64 and anti-CD16 mAb, as performed here, identified four different subsets. The CD64(-) subset consists of CD64(-) / 16(+) cells with high antigen-presenting cell (APC) function and macrophage-like phenotype, and a CD64(-) / 16(-) subset of less active APC but which exhibits a higher mixed lymphocyte reaction (MLR) stimulating and IFN-alpha-producing capacity, possibly resembling plasmacytoid dendritic cell type II (DC2) blood precursors. As well as the majority of CD64(+) cells that appeared CD64(+) / 16(-) and represent typical low-accessory, CD14(high) Mo, we could identify and describe a novel minor subset of CD64(+) / 16(+) cells which is unique in combining typical DC and Mo characteristics in the same cell. These are high IL-12 production, high accessory capacity for antigen- or allogen-activated lymphocytes, and high expression of HLA-DR, CD86, and CD11c.

The platelet-derived neutrophil-activating peptide 2 (NAP-2, 70 amino acids) belongs to the ELR+ CXC subfamily of chemokines. Similar to other members of this group, such as IL-8, NAP-2 activates chemotaxis and degranulation in neutrophils (polymorphonuclear [PMN]) through chemokine receptors CXCR-1 and CXCR-2. However, platelets do not secrete NAP-2 as an active chemokine but as the C-terminal part of several precursors that lack PMN-stimulating capacity. As we have previously shown, PMN themselves may liberate NAP-2 from the precursor connective tissue-activating peptide III (CTAP-III, 85 amino acids) by proteolysis. Instead of inducing cell activation, continuous accumulation of the chemokine in the surroundings of the processing cells results in the down-regulation of specific surface-expressed NAP-2 binding sites and in the desensitization of chemokine-induced PMN degranulation. Thus, NAP-2 precursors may be regarded as indirect mediators of functional desensitization in neutrophils. In the current study we investigated the biologic impact of another major NAP-2 precursor, the platelet basic protein (PBP, 94 amino acids). We show that PBP is considerably more potent than CTAP-III to desensitize degranulation and chemotaxis in neutrophils. We present data suggesting that the high desensitizing capacity of PBP is based on its enhanced proteolytic cleavage into NAP-2 by neutrophil-expressed cathepsin G and that it involves efficient down-regulation of surface-expressed CXCR-2 while CXCR-1 is hardly affected. Correspondingly, we found PBP and, less potently, CTAP-III to inhibit CXCR-2– but not CXCR-1– dependent chemotaxis of neutrophils toward NAP-2. Altogether our findings demonstrate that the anti-inflammatory capacity of NAP-2 is governed by the species of its precursors.

Lipopolysaccharide (LPS), also known as endotoxin, is a compound of the cell wall of Gram-negative bacteria, which has been demonstrated to induce inflammatory reactions in vitro as well as in vivo, including lethal shock. A great number of different cells have been documented to be reactive to LPS, e.g. monocytes/macrophages, vascular cells, polymorphonuclear cells, and even B lymphocytes. We have now established that T lymphocytes could also contribute to an inflammatory reaction to LPS. LPS is a potent inducer of human T-lymphocyte proliferation and cytokine production. The activation of T lymphocytes by LPS requires direct cell-to-cell contact with viable accessory monocytes. This interaction was found to be MHC-unrestricted, but strongly dependent on costimulatory signals provided by B7/CD28 interactions. The frequency of responding T lymphocytes is less than 1:1000. A very exciting finding was that not only monocytes, but also CD34+ hematopoietic stem cells, which circulate in peripheral blood in very low frequency, exert essential accessory cell activity during stimulation of T lymphocytes by LPS. In contrast, the response of T lymphocytes to conventional recall antigens is not controlled by blood stem cells. These conclusions are based on the observation that depletion of CD34-positive blood stem cells resulted in a complete loss of LPS-induced T-lymphocyte stimulation. Addition of CD34-enriched blood stem cells led to a recovery of reactivity of T lymphocyte to LPS. The characteristics of T-lymphocyte activation indicate that LPS is neither active as a mitogen, or as a superantigen, or as a classical antigen, but may activate T lymphocyte through a new, so far undescribed, mechanism. Furthermore, the involvement of hematopoietic blood stem cells in the activation of T lymphocytes by LPS demonstrates a role of these cells in inflammatory and immunological events.

Although platelet factor 4 (PF-4) and the beta-thromboglobulin (beta-TG) proteins represent the first chemokines to be discovered, their functional roles in host defense became clear only recently. Residing in platelets as storage proteins and becoming released into the blood at very high concentrations, these mediators appear to fulfill different and complementary tasks as first-line mediators in the recruitment and activation of leukocytes, as well in the regulation of tissue repair. Whereas both proteins are structurally closely related members of the CXC chemokine subfamily, they are subject to quite dissimilar regulatory mechanisms controlling their generation and their spectrum of biological activities. Thus, proteolytic processing of inactive precursors plays a decisive role in whether the beta-TG proteins will act as stimulatory or inhibitory agents in neutrophil activation via the G protein-coupled receptors CXCR-1 and 2. PF-4, existing as a single molecular form, is largely resistant to proteolytic modification, but its interaction with an unusual receptor(s) on leukocytes (a proteoglycan) appears to depend on its oligomeric state. There is growing evidence that both chemokines may interfere with each other at various regulatory levels to promote coordinated cell activation. Moreover, recent findings suggest novel and unexpected activities for these chemokines, which may extend our view on early host defense.

Tumor regression induced in cancer patients by local instillation of bacillus Calmette-Guérin (BCG) into the bladder is considered to be mediated by cellular immune and inflammatory reactions. In an attempt to elucidate which of these effects are relevant to tumoricidal activity, an in vitro system was employed in which the immunostimulatory effects of BCG could be studied. This report describes the induction of BCG-activated killer (BAK) cells, which effectively lyse bladder tumor cells. Human peripheral blood mononuclear cells (PBMC) were stimulated with viable and sonicated BCG (v-BCG and s-BCG, respectively) to generate BAK cells. Cytotoxicity of BAK cells was comparable with the cytotoxicity exerted by lymphokine-activated killer (LAK) cells generated by interferon (IFN)-gamma but did not reach the level of interleukin-2 (IL-2)-generated LAK cells. Induction of BAK cells was possible only with v-BCG and not with s-BCG. By depletion and enrichment of defined cell populations, the cytotoxic potential of BAK cells could be attributed to a population of CD8(+) and CD56(+) double-positive lymphocytes. Macrophages and CD4(+) cells were required for the induction of killing activity but had no such activity by themselves. Furthermore, the presence of IFN-gamma and IL-2 in the supernatants harvested during the generation of BAK cells was demonstrated. Monoclonal antibodies neutralizing these cytokines abolished BCG-mediated cytotoxicity. From these results, it is concluded that the known beneficial effect of local instillation of BCG on maintenance of the relapse-free state in superficial bladder cancer may be due to local generation of BAK cells.

The G protein-coupled CXC-chemokine receptor CXCR-2 mediates activation of neutrophil effector functions in response to multiple ligands, including IL-8 and neutrophil-activating peptide 2 (NAP-2). Although CXCR-2 has been successfully cloned and expressed in several cell lines, the molecular properties of the native neutrophil-expressed receptor have remained largely undefined. Here we report on the identification and characterization of distinct CXCR-2 glycoforms and their subcellular distribution in neutrophils. Immunoprecipitation and Western blot analyses of surface-expressed receptors covalently linked to IL-8 or NAP-2 as well as in their unloaded state revealed the occurrence of a single CXCR-2 variant with an apparent size of 56 kDa. According to deglycosylation experiments surface-expressed CXCR-2 carries two N-linked 9-kDa carbohydrate moieties that are both of complex structure. In addition, two other CXCR-2 variants of 38 and 40 kDa were found to occur exclusively intracellular and to carry N-glycosylations of high mannose or hybrid type. These receptors did not participate in ligand-induced receptor trafficking, while surface-expressed CXCR-2 was internalized and re-expressed following stimulation with NAP-2. By enzymatic removal of one 9-kDa carbohydrate moiety in surface-expressed CXCR-2 we can show that neither NAP-2-induced trafficking nor signaling of the receptor is dependent on its full glycosylation. Instead, glycosylation was found to protect CXCR-2 from proteolytic attack, as even partial deglycosylation is associated with serine protease-mediated disappearance of the receptor from the neutrophil surface. Thus, although not directly involved in signaling, glycosylation appears to be required to maintain neutrophil responsiveness to CXC-chemokines during inflammation.

Phagocytosis and killing of microorganisms by reactive oxygen radicals are important defence mechanisms of the immune system and it was shown that human monocytes (MO) are heterogeneous in exerting these functions. Previously, we described that human peripheral blood MO consist of a major subset of Fcγ-receptor-I (CD64)-positive cells exhibiting low accessory cell capacity but high phagocytic activity, and a minor subset of CD64-negative cells with dendritic cell (DC)-like high T cell accessory cell capacity but low phagocytic capacity. Recently, we could show that each subset itself further differs in the expression of the Fcγ-receptor-III (CD16) and T cell accessory activities resulting in four different subsets: two CD16 + subsets (CD64 + or CD64 - ) with high T cell stimulation capacity and two CD16 - subsets (CD64 + or CD64 - ) with low accessory activities. In the present study we demonstrate that these subsets also differ in their ability to phagocytose opsonized bacteria ( S. aureus and E. coli ) and in the generation of reactive oxygen species. Both CD64 + subsets (CD16 + or CD16 - ) exhibit high phagocytic activity accompanied by intracellular superoxide induction. Luminal-dependent (mainly myeloperoxidase (MPO)-mediated) chemiluminescence (CL) response to latex and FMLP (formylmethionylleucylphenylalanine) was also high in these cell populations. Phagocytic activity and modest CL response was shown in CD64 - /CD16 + but not in CD64 - /CD16 - cells, indicating that each subset except for CD64 - /CD16 - cells may engulf bacteria and exhibit MPO activity. Taken together, these data demonstrate further heterogeneity of peripheral blood MO in both, phagocytic activity and generation of reactive oxygen species indicating differences between the four subsets in this kind of defence mechanisms against pathogens.

Unstimulated monocytes rapidly undergo physiological changes resulting in programmed cell death (apoptosis) while stimuli promoting differentiation of these cells into macrophages were shown to inhibit apoptotic processes. In the present study, we report that the platelet-derived alpha-chemokine platelet factor 4 (PF4) induces the differentiation of monocytes into macrophages, as is evident from morphological changes as well as from the up-regulation of differentiation markers (carboxypeptidase M/MAX1 and CD71). Significant alterations of the phenotype were observed after 72 hours of culture in the presence of the chemokine and required a minimal concentration of 625 nmol/L PF4. PF4-induced macrophages were characterized by a lack of HLA-DR antigen on their surface but showed a strong increase in the expression of the CD28 ligand B7-2. Furthermore, PF4 stimulation prevented monocytes from undergoing spontaneous apoptosis during 72 hours of culture as determined in an annexin-V-binding assay. Although PF4 induced the secretion of relevant amounts of TNF-alpha, neutralizing antibodies directed against TNF-alpha or granulocyte-macrophage colony-stimulating factor (GM-CSF) did not revert PF4-induced rescue from programmed cell death, suggesting that PF4 exerts its antiapoptotic effects in a TNF-alpha- or GM-CSF-independent fashion. On the basis of these results, we propose a novel role for PF4 in the control of monocyte differentiation during an inflammatory process in vivo. (Blood. 2000;95:1158-1166)

We studied 32 HIV-seronegative patients with pulmonary disease caused by nontuberculous mycobacteria (NTM). Immunologic studies included lymphocyte subset analysis by flow cytometry, measurement of interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α) production followingin vitro stimulation of diluted whole blood (DWB) and peripheral blood mononuclear cells (PBMC) by phytohemagglutinin (PHA), anti-CD3 as well as purified protein derivative of tuberculin (PPD), and in four cases with different amounts of the very mycobacterium, which caused disease in these patients. Data were compared to those of 30 HIV-seronegative patients with disease byMycobacterium tuberculosis (MTb). Following α-CD3-stimulation of PBMC, NTM patients showed lower IFN-γ(P < 0.00005) and lower TNF-α(P < 0.02). For a subgroup of tuberculin skin test-positive NTM patients we found significantly lower PPD-induced IFN-γ releases in cultured DWB(P < 0.0002) and PBMC(P < 0.0004) compared to MTb patients. Data for PPD-induced TNF-α release for this subgroup were also significant(P < 0.001 andP < 0.05, respectively). The four NTM patients with poor PPD-induced IFN-γ response hardly showed increased cytokine production on stimulation with their specific mycobacterium. The lower production capacity of IFN-γ and TNF-α of NTM patients compared to the MTb patients points to an immunologic imbalance forming the basis for their increased susceptibility to pulmonary infections by nontuberculous mycobacteria.

Platelet factor 4 (PF-4), a member of the CXC-subfamily of chemokines, is secreted in high amounts by activated platelets. In previous studies, we found that PF-4 specifically binds to human polymorphonuclear granulocytes (PMN), but requires tumor necrosis factor- (TNF-) as a costimulus for the induction of effector functions in suspended cells. In the present study, we have examined PF-4 in comparison with interleukin-8 (IL-8) for its ability to promote interaction of PMN with cultured endothelial cells (EC). We show here for the first time that PF-4 dose-dependently induces PMN to undergo extremely firm adhesion to EC as well as to exocytose secondary granule contents in the presence of these cells. Interestingly, costimulation by TNF- was not required, indicating that EC could provide a corresponding signal(s). As evident from antibody blocking experiments, PF-4–induced adhesion involved PMN-expressed L-selectin as well as leukocyte function-associated molecule-1 (LFA-1), whereas IL-8 involved MAC-1. Because blocking antibodies to LFA-1 but not to L-selectin or MAC-1 abrogated PF-4–dependent marker exocytosis from PMN, the costimulatory signal provided by EC appears to be elicited through cell-cell contact via LFA-1. IL-8, inducing the upregulation of MAC-1, did not elicit marker exocytosis in contact with EC. Our results suggest a role for PF-4 in the promotion of PMN-EC interaction that is virtually different from that exhibited by other CXC-chemokines such as IL-8.

The prerequisites for the initiation of pathophysiological effects of endotoxin (lipopolysaccharide [LPS]) include binding to and possibly internalization by target cells. Monocytes/macrophages are prominent target cells which are activated by LPS to release various pro- and anti-inflammatory mediators. The aim of the present study was to establish a new method to determine the binding and internalization rate of different LPS chemotypes by human monocytes and to correlate these phenomena with biological activity. It was found that membrane-bound LPS disappears within hours from the surface being internalized into the cell. Further, a correlation between the kinetics of internalization and the length of the sugar chain as well as an inverse correlation between the time course of internalization and LPS hydrophobicity was revealed. Comparison of the internalization kinetics of different LPS chemotypes with kinetics of tumor necrosis factor alpha release and kinetics of oxidative burst did not reveal any correlation of these parameters. These findings suggest that cellular internalization of and activation by LPS are mechanisms which are independently regulated.

The activation of immunocompetent cells by lipopolysaccharide (LPS) during severe Gram-negative infections is responsible for the pathophysiological reactions, possibly resulting in the clinical picture of sepsis. Monocytes recognize LPS mainly through the LPS receptor CD14, however, other cellular binding structures have been assumed to exist. In previous studies, we have described an 80-kDa LPS-binding membrane protein (LMP80), which is present on human monocytes as well as endothelial cells. Here we demonstrate that LMP80 is widely distributed and that it formes complexes together with LPS and sCD14. Furthermore, we report on the biochemical purification of LMP80 and its identification as decay-accelerating factor, CD55, by amino acid sequencing and cloning techniques. Our results imply a new feature of CD55 as a molecule which interacts with LPS/sCD14 complexes. However, the involvement of CD55 in LPS-induced signaling remains to be elucidated.

CD34+ hematopoietic stem cells, which circulate in peripheral blood with very low frequency, exert essential accessory function during lipopolysaccharide (LPS)-induced human T lymphocyte activation, resulting in interferon γ production and proliferation. In contrast, stimulation of T cells by “conventional” recall antigens is not controlled by blood stem cells. These conclusions are based on the observation that depletion of CD34+ blood stem cells results in a loss of LPS-induced T cell stimulation as well as reduced expression of CD80 antigen on monocytes. The addition of CD34-enriched blood stem cells resulted in a recovery of reactivity of T cells and monocytes to LPS. Blood stem cells could be replaced by the hematopoietic stem cell line KG-1a. These findings may be of relevance for high risk patients treated with stem cells or stem cell recruiting compounds and for patients suffering from endotoxin-mediated diseases.

The neutrophil agonist neutrophil-activating peptide-2 (NAP-2) arises through proteolytic processing of platelet-derived N-terminally extended inactive precursors, the most abundant one being connective tissue-activating peptide-III (CTAP-III). Apart from N-terminal processing, C-terminal processing also appears to participate in the functional regulation of NAP-2, as indicated by our recent identification of an isoform missing four C-terminal amino acids, NAP-2 (1–66), which was about threefold more potent than full-size NAP-2. In the present study, we report on the discovery and identification of natural NAP-2 (1–63), an isoform truncated by seven C-terminal residues. Functional and receptor-binding analyses demonstrated that NAP-2 (1–63) represents the most active isoform, being about fivefold more potent than full-size NAP-2. Analyses of rNAP-2 isoforms successively truncated at the C terminus by up to eight residues suggest functionally important roles for acidic residues and for the leucine at position 63, a residue highly conserved within CXC chemokines. Finally, we report on a novel C-terminally truncated isoform of CTAP-III (CTAP-III (1–81)) representing the potential precursor of NAP-2 (1–66). We show that C-terminal truncation in CTAP-III enhances its potency to desensitize chemokine-induced neutrophil activation, indicating that C-terminal processing might not only serve to enhance neutrophil activation, but might as well participate in the down-regulation of an inflammatory response.

In a previous study using the monoclonal anti-CD26 antibody MIB-DS2/7 in leprosy and other granulomatous diseases, it was shown that CD26 may be a candidate for use as an operational marker of a human Th1-like reaction. In this follow-up study, we compared seven different monoclonal anti-CD26 antibodies with respect to their staining pattern in lepromatous and tuberculoid leprosy tissues. Three distinct staining patterns became apparent in this anti-CD26 antibody panel: staining of T-lymphocytes and of connective tissue; staining of T-lymphocytes, connective tissue and macrophages; and almost no staining of T-lymphocytes but staining of connective tissue and macrophages. The two antibodies assigned to the first staining pattern, including MIB-DS2/7, were found to be most suitable for the operational discrimination between Th1-like and Th2-like reactions in leprosy. The antibodies assigned to staining patterns 2 and 3 did not allow this discrimination. Although all seven monoclonal antibodies investigated were specific for CD26, only two were found to be useful in identifying a Th1-like immune reaction in human tissue.

Recently, we have shown that LPS is a potent inducer of human T cell proliferation and lymphokine production. However, the activation of T cells by LPS has been demonstrated to be monocyte dependent and to require direct cell-to-cell contact. Here, we investigated the role of monocytes as accessory cells and the requirement for costimulatory signals in more detail. We found that the accessory cell activity of monocytes during LPS-induced T cell proliferation is characterized by the following features: LPS-primed monocytes are competent stimulators of T cell proliferation; interaction of LPS with monocytes during the priming step is dependent on CD14 and is sensitive to ammonia; monocyte/T cell interactions are not MHC restricted but are strongly dependent on interactions of CD28 and/or CTLA-4 on T cells and their ligands CD80 and/or CD86 on monocytes. CD80 seems to be crucial for the activation of T cells by monocytes, since monocytes expressing CD86 but not CD80 after LPS stimulation were unable to stimulate T cells; IL-12, at least as a costimulatory factor, but not IL-15, is important in LPS-induced T cell proliferation. Taken together, our results indicate that LPS acts neither as a mitogen, nor as a superantigen, nor as an Ag. The activation of human T cells by LPS requires the help of accessory functions by primed monocytes and is MHC unrestricted but needs costimulatory signals via CD28 and/or CTLA-4.

Surface structures of bacteria contribute to the microbial pathogenic potential and are capable of causing local and generalized inflammatory reactions. Among these factors, endotoxin and peptidoglycan are of particular medical importance. Both toxic bacterial polymers are now recognized to interact with the same cellular receptor, the CD14 molecule, which is expressed on different types of immune cells, in particular, monocytes/macrophages. The interaction between these bacterial activators and CD14 leads to the production of endogenous mediators such as tumor necrosis factor alpha, interleukin 1 (IL-1), and IL-6, which are ultimately responsible for phlogistic responses. The fact that CD14 recognizes not only endotoxin and peptidoglycan but also other glycosyl-based microbial polymers suggests that this cellular surface molecule represents a lectin.

In this study we describe a general method for the detection and characterization of endotoxin-(lipo-polysaccharide, LPS)-binding membrane proteins. In the past, experimental procedures to detect LPS-binding sites on cells were generally performed with chemically modified LPS derivates. Since anymodification of a ligand may lead to a modification of its binding characteristics, the results of thosestudies are controversial.In our assay, cell membrane preparations are treated with free lipid A, the endotoxic center of LPS,in the presence of normal human serum. After binding of lipid A, membrane proteins are solubilized bymild detergent treatment without disruption of the lipid A-protein complexes. Addition of anti-(lipid A)mAbs and subsequent adding of protein A agarose lead to the precipitation of complexes of lipid A andits binding proteins. By SDS/PAGE and western blot, these precipitates can be screened for the presenceof LPS/lipid A-binding proteins. We describe the use of this method for the immuno-coprecipitation oflipid A (or LPS) with an 80-kDa LPS-binding membrane protein (LMP80), which we have previouslyidentified on several human cells. In addition, CD14, the well-known functional LPS receptor on mono-cytes and macrophages, can be detected.By means of this immuno-coprecipitation approach we could demonstrate binding of either purifiedLPS preparations or synthetic lipid A to these LPS/lipid A-binding membrane proteins at physiologicalpH under conditions in which the proteins are in their natural membranous environment.Keywords: lipopolysaccharide; lipopolysaccharide-binding protein; CD14; anti-lipopolysaccharide anti-body; 80-kDa lipopolysaccharide-binding membrane protein (LMP80).Lipopolysaccharides (LPS, endotoxin) constitute the major biological activity and, therefore, a putative LPS-binding mole-component of the outer membrane of gram-negative bacteria. cule should also bind lipid A. In the immuno-coprecipitationLPS are responsible for many pathophysiological effects ob- assay we incubated cell membrane preparations, which containserved during gram-negative septic episodes [1, 2]. The LPS of the proteins in their native conformation, with lipid A. Afterall families of gram-negative bacteria contains the highly con- binding of lipid A to the LPS-binding molecules, the cell mem-served lipid part termed lipid A, which is able to mimic the branes were washed several times and solubilized by mild de-biological effects of LPS [1, 3]. Thus, lipid A represents the tergent lysis without disruption of the lipid A-protein complexes.endotoxic center of LPS. These complexes were precipitated by addition of anti-(lipid A)Many experimental procedures for the detection of the cellu- mAbs together with protein A agarose beads. After some wash-lar targets of LPS in host cell membranes have been carried out ing steps the precipitates were eluted by adding SDS sampleunder non physiological circumstances: Either the LPS prepara- buffer (62.5 mM Tris, 80 mM dithiothreitol,10% glycerol, 2%tion was chemically modified by labeling with or substitution SDS, 0.002% Bromophenol blue, pH 6.8) and separated by SDS/for a cross-linker, or the proteins under investigation were not PAGE. Specific proteins were detected by an immunoblot tech-in their physiological conformation after SDS/PAGE and west- nique on nitrocellulose membrane. The immuno-coprecipitationern blot techniques. Modification of a receptor molecule or its method not only leads to the detection of LPS-binding proteins,ligands for binding studies is critical, as the modification may it also permits the enrichment of those molecules from cellhave a strong influence on the binding behaviour. Therefore, the membrane preparations.physiological relevance of many molecules found by the use of Here, we demonstrate the successful use of this method bythose techniques remains controversial. the identification of lipid A binding to an 80-kDa LPS-bindingTo obtain a more physiological detection system for LPS- membrane protein (LMP80), which was previously described bybinding molecules we developed an immuno-coprecipitation our group [4] as well as to the LPS receptor CD14. Furthermore,assay with free lipid A and anti-(lipid A) antibodies. Lipid A we examined the binding of LPS as well as synthetic oligoacylwas used, because it is the minimal structure of LPS with full lipid A partial structures to LMP80 [527].

The CXC-chemokines interleukin-8 (IL-8), neutrophil-activating peptide-2 (NAP-2), and melanoma growth-stimulatory activity (MGSA) are chemoattractants with high selectivity for neutrophils. Although IL-8 has been shown to act as an extremely potent mediator, reports on NAP-2 and MGSA are still contradictory. Here we show for the first time that NAP-2 and MGSA induce two distinct optima of neutrophil chemotaxis. A first optimum is elicited within a concentration range as low as it is characteristic for IL-8. However, a second optimum appears at more than 200-fold higher stimulus concentrations, at which IL-8 is inactive. Investigating the involvement of the two chemokine receptors CXCR-1 and CXCR-2 in NAP-2–mediated chemotaxis, we observe that the cells become desensitized to the first optimum of the chemokine after selective downregulation of CXCR-2, while both optima disappear upon simultaneous downregulation of both receptors. Blocking monoclonal antibodies (MoAbs) specific for CXCR-2 or CXCR-1 either suppress the first optimum of NAP-2–induced chemotaxis or drastically reduce the second one, respectively. These results provide evidence that both receptors are involved in NAP-2–induced neutrophil chemotaxis, with CXCR-2 rendering the cells responsive to low dosages of the chemokine, and with CXCR-1 extending their responsiveness to NAP-2 dosages higher by several orders of magnitude.

Inflammation contributes to a variety of arterial diseases including atherosclerosis. Interleukin 1beta (IL-1beta) in its activated mature 17-kDa form may mediate aspects of vascular inflammation. As shown previously, human vascular wall cells, such as smooth muscle cells (SMC), express the IL-1beta precursor upon stimulation and the IL-1beta-converting enzyme (ICE) constitutively but do not produce mature IL-1beta or express ICE activity. How SMC, the most numerous cell type in arteries, may release active IL-1beta has therefore remained a perplexing problem. We report here that stimulation of human vascular SMC and endothelial cells (EC) through CD40 ligand, a mediator recently localized in human atheroma, induced elaboration of the IL-1beta precursor as well as activation of cell-associated ICE. In addition to the constitutively expressed 45- and 30-kDa immunoreactive ICE proteins, vascular cells incubated with recombinant human CD40 ligand (rCD40L) (but not IL-1 or TNF) showed an increase of a 20-kDa immunoreactive ICE protein by Western blot analysis. Furthermore, SMC and EC stimulated through rCD40L processed recombinant human IL-1beta precursor (pIL-1beta), generating a cleavage product of approximately 17 kDa. Appearance of both the 20-kDa immunoreactive ICE protein and pIL-1beta processing activity required at least 6 h of stimulation with 0.3 or 1.0 microg/ml rCD40L, respectively, and was inhibited by pre-incubation of the ligand with an anti-CD40L antibody. Stimulation of vascular SMC and EC through rCD40L resulted in the release of biologically active IL-1beta, indicating processing of the native IL-1beta precursor induced by the ligand. These findings establish a novel mechanism of IL-1beta activation in human vascular cells and, moreover, indicate a new pathway of ICE-activation, which could participate in inflammatory aspects of atherogenesis and other disease states.

Multinucleated giant cells (MGCs) are a key feature of granulomas. They have been studied with respect to the mechanism and regulation of their formation, but the function of these cells still remains elusive. A new method for the in vitro generation of granulomas was developed and characterized in which L3 larvae of Nippostrongylus brasiliensis, as a target for the cellular response, were co-incubated with human mononuclear blood cells. The development of epithelioid cells and MGCs was observed and single isolated MGCs were analysed by the reverse transcriptase polymerase chain reaction method. The presence of tumour necrosis factor alpha (TNFα), interleukin-1 beta (IL-1β), interleukin-6 (IL-6), and inducible nitric oxide synthase (iNOS) transcripts in MGCs was demonstrated. It is proposed that MGCs in the granuloma model may in part represent an active cellular constituent involved in granuloma formation and turnover and in the destruction of the irritant. © 1997 John Wiley & Sons, Ltd.

Local immunoregulatory processes during normal vascular biology or pathogenesis are mediated in part by the production of and response to cytokines by vessel wall cells. Among these cytokines interleukin (IL)-1 is considered to be of major importance. Although vascular smooth muscle (SMC) and endothelial cells (EC) expressed both IL-1alpha and IL-1beta as cell-associated, 33-kilodalton (kD) precursors, SMC neither contained detectable mature IL-1beta, nor processed recombinant IL-1beta precursor into its mature 17-kD form. Thus, we investigated the expression and function of IL-1beta-converting enzyme (ICE) in vascular cells. We demonstrate in processing experiments with recombinant IL-1 precursor molecules that EC processed IL-1beta, in contrast to SMC. Despite the failure of SMC to process IL-1beta, these cells expressed ICE mRNA, immunoreactive ICE protein, and the expected IL-1beta nucleotide sequence. The lack of processing was explained by our finding that extracts of SMC specifically and concentration dependently blocked processing of IL-1beta precursor by recombinant or native ICE. The initial biochemical characterization of the inhibitory activity showed that it is heat-labile, has a molecular size of 50-100 kD, and is associated to the cell membrane compartment. Inhibition of processing, i.e., activation of IL-1beta precursor by SMC may constitute a novel regulatory mechanism during normal vascular biology or pathogenesis of vascular diseases.

Colony-stimulating factors (CSF) are used clinically in the treatment of chemotherapy-induced myelosuppression and in support of bone marrow transplantation. As CSF are known to have pleiotropic functions, their effects on cellular cytotoxicity were analysed in vitro against bladder carcinoma cell lines. By means of an L-[3H]methionine-release assay, the cytotoxicity of peripheral blood mononuclear cells against the natural-killer(NK)-cell-resistant bladder carcinoma cell lines BT-A and SBC-7 was measured using different effector/target-cell ratios. Costimulatory effects of granulocyte-colony-stimulating factor (G-CSF), granulocyte/macrophage colony-stimulating factor (GM-CSF), interleukin-3 (IL-3) and stem cell factor (SCF) on the generation of lymphokine-activated killer (LAK), bacillus Calmette-Guérin-activated killer (BAK) and natural killer (NK) cell cytotoxicity were investigated in this assay. Furthermore, the effect of CSF on proliferation of urothelial tumor cells in vitro was determined by a [3H]thymidine DNA-labelling technique. GM-CSF, but not G-CSF, IL-3 or SCF, was able to increase NK, BAK and LAK cytotoxicity in a dose-dependent manner. No acceleration of carcinoma cell proliferation was evident under the conditions of our assay. These data indicate the costimulatory effect of GM-CSF on cellular cytotoxicity, which might be used for immunotherapeutic purposes.

Lipopolysaccharides (LPS, endotoxin) stimulate mononuclear cells to release cytokines which initiate endotoxic effects. Interaction of LPS at low concentrations with target cells is CD14-independent whereas at high LPS concentrations it is CD14-independent. Here, we demonstrate by resonance energy transfer (RET) technique that nonspecific, CD14-independent intercalation of LPS into membrane systems can be mediated by lipopolysaccharide-binding protein (LBP). It is proposed that in this pathway, LBP breaks down LPS aggregates, transports the smaller units to and inserts them into the phospholipid cell matrix. We furthermore show that LBP also mediates the intercalation of other negatively charged amphiphilic molecules. We propose a model explaining CD14-independent cell activation at high endotoxin concentrations.

The interaction of CD28 with its ligands is important for T-cell activation. Recent studies demonstrated the existence of at least two ligands on accessory cells, CD80 (B7-1) and CD86 (B7-2). In this study we demonstrate that, although CD80 and CD86 are both expressed on monocytes, they seem to have different functions. Freshly isolated monocytes express CD86 but are CD80-negative. CD80 expression is weakly induced after 6-8 hr of in vitro culture and is enhanced by stimulation. CD86 expression is enhanced faster than CD80 expression and reaches the peak level after 4-6 hr in stimulated cells. Reverse transcription-polymerase chain reaction studies demonstrate that freshly isolated monocytes contain no CD80-mRNA. The mRNA of CD80 is induced after 4-6 hr of culture, which matches with the expression of the protein. Inhibition studies using different antibodies against both molecules and the fusion protein CTLA4Ig show that only anti-CD80 and CTLA4Ig could partially inhibit antigen-specific (tuberculin) and polyclonal (anti-CD3) lymphoproliferation and interferon-gamma (IFN-gamma) secretion of T cells cocultured with autologous monocytes. IFN-gamma secretion was more sensitive to blocking costimulation than proliferation. The antibody BB-1 did not inhibit proliferation and cytokine secretion, nor did the anti-CD86 clone IT2.2. CTLA4Ig, which binds both CD80 and CD86, has the same inhibitory capacity as the anti-CD80 antibody tested. From those findings we conclude that human monocytes use CD80 as a costimulatory ligand for CD28 and utilize other costimulatory mechanisms besides those mediated via molecules of the B7 family.

Blood monocytes represent a heterogeneous cell population with respect to phenotype and function. We have previously described that a minor subset of Fcγ receptor I-negative (CD64−) monocytes, comprising < 10% of all monocytes, exhibits a significantly higher accessory capacity in allogeneic or purified protein derivative (PPD) of tuberculin-induced T cell activation than the majority of CD64-expressing (CD64+) monocytes. CD64− monocytes were also found to represent the major source of Newcastle disease virus (NDV)-induced interferon (IFN)-α within human monocytes. In the present study we demonstrate that CD64− monocytes are also the main producers of IFN-α in response to Herpes simplex virus type 1 (HSV-1) or influenza (type A) antigens. The virus-induced IFN-α release by monocytes, but mainly that by CD64− monocytes, can be further increased by co-culture with autologous T cells, which alone do not produce significant amounts of IFN-α in response to virus. In addition, CD64− and CD64+ monocytes also differ in their accessory capacity in virus-induced T cell responses. CD64− monocytes exposed to influenza antigens induced higher IFN-γ release and proliferation by the responding autologous T cells than virus-exposed CD64+ monocytes. In virus-stimulated monocyte/T cell co-cultures, CD64− monoyctes also induced larger size cell clusters than CD64+ monocytes, indicating direct cell-to-cell interaction with a higher number of T cells, which represent the main component of these clusters.

Dipeptidyl peptidase IV (DP IV, CD26), known as an activation marker of T lymphocytes, is a proline-specific protease thought to be involved in the regulation of the immune response. The physiological role of dipeptidyl peptidase IV in the immune system and the molecular events of lymphocyte activation mediated by this enzyme are only partly established. Former results suggested the occurrence of different molecular forms of DP IV in distinct human sources. As yet it has been unknown whether DP IV from human hematopoetic cells also appears in different forms and whether similar structural modifications are involved in functional processes of the regulation of the immune response. Here we describe that lymphocytic DP IV/CD26 occurs in various molecular forms and that some of them are associated with the activation process. In cell lysates of mitogen-activated lymphocytes at least 5 enzymatically active DP IV forms and up to 11 immunoreactive molecular forms of this enzyme with isoelectric points between pH 3.5 and 5.9 were discernible. Corresponding analyses of soluble and membrane cell fractions of human lymphocytes showed significant differences in the staining pattern of molecular DP IV structures. After mitogenic stimulation a special molecular form of DP IV arises in the membrane, which was originated either from the soluble part of the cell (translocation) or represents a new synthesized form. Particularly, changes of molecular DP IV forms after mitogenic stimulation strongly suggest that special forms/epitopes of this enzyme are directly involved in the process of lymphocyte activation and growth. Importantly, different monoclonal DP IV antibodies partly define different molecular forms of DP IV. Moreover, the pattern of immunostaining and enzymatic staining (Gly-Pro-β-methoxynaphtylamide) also reveals drastic differences. These data strongly suggest a direct relationship between the expression/recognition of special DP IV epitopes and the contradictory functional effects of monoclonal DP IV antibodies found by us and other groups.

A PCR method is described for determining the expression of multiple heterogeneous mRNAs from single cells. The total mRNA pool of a single selected cell is subjected to reverse transcription and subsequent tailing with poly(dA). This cDNA is preamplified by a sequence non-specific PCR protocol using oligo(dT)-containing primers. The single cell cDNA library obtained permits the analysis of virtually unlimited numbers of mRNA species per cell using sequence-specific PCR. This procedure of multiple mRNA analysis enables phenotyping of any cell for its mRNA composition and could be used to study the cytokine mRNA expression of individual human T cells ex vivo. The method should greatly facilitate the analysis of combinatorial expression of known genes in any cell.

Activation of cells by bacterial lipopolysaccharide (LPS) plays a key role in the pathogenesis of gram-negative septic shock. The 55-kDa glycoprotein CD14 is known to bind LPS and initiate cell activation. However, there must be additional LPS receptors because CD14 is linked by a glycosylphosphatidyl inositol anchor to the cell membrane and therefore unable to perform transmembrane signalling. Searching for potential LPS receptors, we investigated the binding of LPS to membrane proteins of the human monocytic cell line Mono-Mac-6. Membrane proteins were electrophoretically separated under reducing conditions, transferred to nitrocellulose, and exposed to LPS, which was visualized with anti-LPS antibody. Smooth- and rough-type LPS, as well as free lipid A, bound to a variety of proteins in the absence of serum. However, in the presence of serum, additional or preferential binding to a protein of approximately 80-kDa was observed. Experiments with differently acylated lipid A structures showed that the synthetic tetraacyl compound 406 was still able to bind, whereas no binding was detected with the bisacyl compound 606. The 80-kDa membrane protein was also detected on human peripheral blood monocytes and endothelial cells. The serum factors mediating the binding of lipid A to the 80-kDa membrane protein were identified as soluble CD14 and LPS-binding protein. From these results, we conclude that this 80-kDa protein is a candidate for the hypothetical molecule for LPS and/or LPS-CD14 recognition and signal transduction.

Recent data provide evidence that antigen-specific CD4+ T-cell clones or antigen-activated T-cell lines can kill antigen-presenting cells (APC). We focused our studies on monocytes acting as APC in cultures of T cells freshly isolated from peripheral blood. The presence of monocytes in culture was monitored by their ability to emit light during phagocytosis of latex particles (latex-induced chemiluminescence). Using this approach as well as flow cytometry, evidence is presented that monocytes are eliminated from cultures with T cells activated with recall antigens (PPD or TT). The mechanism of monocyte elimination involved apoptosis as judged from in situ detection of DNA strand breaks by the terminal deoxynucleotidyl transferase assay. The antigen- but not lectin-dependent monocyte elimination was MHC-restricted and mediated by CD4+ T lymphocytes. This finding supports the hypothesis that elimination of APC is a general phenomenon during T-cell activation and may represent an important immunoregulatory mechanism.

During infection or inflammation, cells of the blood vessel wall, such as endothelial cells (EC) and smooth muscle cells (SMC), contribute to the regulation of the immune response by production of cytokines or expression of adhesion molecules. Little is known about the mechanism(s) involved in the stimulation of vascular cells by endotoxin (lipopolysaccharide [LPS]). As reported previously, LPS antagonists reduce LPS-induced cytokine production or adhesion in vitro specifically, suggesting a specific LPS recognition mechanism. We thus investigated the role of CD14 for stimulation of vascular SMC by LPS. Complement-fixing antibodies directed against CD14 (LeuM3, RoMo I, or Mo2) lysed monocytes but failed to mediate lysis of EC or SMC, indicating the lack of endogenous membrane CD14 in vascular cells. In addition, we did not detect expression of CD14 protein on EC and SMC in cell sorting analysis or cell immunoassay experiments. These observations are in line with our finding that a CD14 probe did not hybridize with mRNA or EC or SMC in Northern (RNA) blot experiments, although it hybridized well with monocyte-derived mRNA. We obtained the same results with the much more sensitive reverse transcription-PCR. Since the vascular SMC did not express endogenous CD14, we investigated the role of human serum-derived soluble CD14 (sCD14) for activation of SMC by LPS. In medium containing human serum, anti-CD14 antibodies inhibited activation of SMC by LPS. In contrast, the same antibodies did not inhibit activation of cells cultured in medium containing fetal calf serum. SMC cultured in sCD14-depleted medium responded 1,000-fold less to LPS than cells cultured in presence of sCD14. Reconstitution of sCD14-depleted serum or supplementation of serum-free medium with recombinant CD14 restored the capacity of the cells to respond to LPS. These results show that specific activation of vascular SMC by LPS does not involve binding to endogenous membrane CD14, but that the activation of vascular SMC by LPS is mediated to a great extent by serum-derived sCD14.

We have previously described a C-terminally truncated variant of the chemokine neutrophil-activating peptide 2 (NAP-2) that exhibited higher neutrophil-stimulating capacity than the full-size polypeptide. To investigate the impact of the NAP-2 C terminus on biological activity and receptor binding, we have now purified the novel molecule to homogeneity. Furthermore, we have cloned, expressed in Escherichia coli, and purified full-size recombinant NAP-2 (rNAP-2-(1-70)) and a series of C-terminally deleted variants (rNAP-2-(1-69) to rNAP-2-(1-64)). Biochemical and immunochemical analyses revealed that the natural NAP-2 variant was structurally identical to the rNAP-2-(1-66) isoform. As compared with their respective native and recombinant full-size counterparts, both molecules exhibited ∼3-4-fold enhanced potency in the induction of neutrophil degranulation as well as 3-fold enhanced binding affinity for specific receptors on these cells. All other variants were considerably less active. The natural occurrence of a NAP-2 variant truncated by exactly four residues at the C terminus suggests that limited and defined proteolysis at this site plays a role in the regulation of the biological function of the chemokine.

To detect mRNA expression of nitric oxide synthase (NOS) isoforms in human monocytes/macrophages reverse transcription polymerase chain reaction (RT-PCR) was used. mRNA was isolated from stimulated or unstimulated monocytes/macrophages and RT-PCR was performed using oligonucleotide primers derived from mRNA sequences of either human endothelial constitutive (c) or human hepatocyte inducible (i) NOS. RT-PCR of mRNA isolated from resting monocytes and macrophages resulted in the amplification of a cNOS specific mRNA fragment. When the cells were stimulated with lipopolysaccharide (LPS)/interferon-gamma (IFN-gamma) prior to mRNA extraction, RT-PCR yielded an iNOS-specific amplification product. Whereas the activation of both cell types was accompanied by expression of iNOS mRNA, the cNOS signal seemed to be diminished upon immunostimulation. Not only in purified human monocytes but also in the human monocytoid cell lines MonoMac 6, THP-1, and U937 cNOS mRNA was detected. The data clearly demonstrate the presence of iNOS and cNOS mRNA in human monocytes/macrophages and provide the necessary tools to investigate the regulation of NO synthesis in these cell populations.

The multifunctional cytokine transforming growth factor-beta 1 (TGF-beta 1) is known to inhibit the proliferation of lymphocytes. However, the role of TGF-beta 1 in the production and secretion of various interleukins is not yet clear. In this study we have analysed in parallel the effects of TGF-beta 1 on both DNA synthesis and production of the cytokines IL-1, IL-2, IL-6, and TNF-alpha by pokeweed mitogen-stimulated peripheral blood mononuclear cells. With this stimulation system we show that TGF-beta 1 at a concentration of 15 ng/ml significantly suppresses IL-2 and IL-6 production. The release of IL-1 and TNF-alpha, however, was not influenced under these conditions. Under similar conditions DNA synthesis of PWM-stimulated PBMC was found to be inhibited by 50 +/- 10%. Using flow cytometric methods we could demonstrate that TGF-beta 1 arrested the cells in the G0/G1 phase of the cell cycle. Taken together, these results suggest that TGF-beta 1 may suppress immune responses by inhibiting the endogenous production of IL-2 and IL-6.

At present, few data are available on intracellular interleukin 2 (IL-2) and its posttranscriptional regulation. Unlike other lymphokines, IL-2 does not accumulate within the cell, but is rapidly secreted following its production. The process of detection and biochemical characterization of intracellular IL-2 involved using a high producer subclone of the Jurkat T-lymphoma line as a source for IL-2, in combination with a two-step separation protocol and a sensitive detection method. Following phytohemagglutinin (PHA) 4β-phorbol 12-myristate 13 acetate (TPA) stimulation, a 14 kDa molecule could be visualized in Western blots by means of two monoclonal anti-IL-2 antibodies possessing different epitope specificities. This molecule exhibited biological activity of IL-2 as determined by a murine cytotoxic T-cell proliferation assay. In addition to this biologically active form of the lymphokine, a strongly immunoreactive protein with a molecular weight of 54 kDa (P54) was found in Jurkat cell lysates. Further biochemical characterization of this intracellular variant revealed an iso-electric point similar to that of secreted forms of IL-2. All attempts to split the 54 kDa molecule into smaller subunits failed, and no biological IL-2 activity could be measured in response to P54. However, the appearance of this high molecular weight variant followed clear-cut time kinetics. The highest concentration of P54 was found to occur after 2 h of stimulation. Thereafter its concentration decreased continuously, while the amount of the biologically active 14 kDa variant increased under ongoing stimulation. One possible explanation for these results is that P54 may represent an immature form of IL-2 that is tightly linked to a carrier molecule.

We investigated the effect of human immunodeficiency virus type 1 (HIV-1) recombinant gp120 (rec.gp120) on phenotype and function of cultured monocytes. Rec.gp120 significantly reduced the accessory function of monocytes to stimulate autologous lymphocytes with anti-CD3, the Fc receptor–mediated chemiluminescence of monocytes, and the expression of CD4 and Fc receptor I/II, while the expression of the monocyte marker GD14 and major histocompatibility complex class I and II was not influenced. According to these phenotypic results, preincubation of monocytes with rec.gp120 depressed anti-CD3 antibody-induced T cell stimulation and Fc receptor-mediated phagocytosis as determined by chemiluminescence. Interferon-γ release of lymphocytes induced by purified protein derivative of tuberculin was enhanced by gp120. These effects of isolated gp120 on monocyte immune functions in vitro might contribute to the understanding of the pathophysiology of HIV-1 infection in viva J. Leukoc. Biol. 55: 545–551; 1994.

Fc gamma receptor I-positive (CD64+) and Fc gamma receptor I-negative (CD64-) monocytes were prepared from highly purified (elutriation-derived) human monocytes by cytofluorograph cell sorting, and a phenotypical and functional dissociation of the isolated CD64+ and CD64- monocyte subsets is demonstrated. Surface analyses revealed that the surface antigen pattern of CD64+ monocytes corresponds to the phenotype of typical unseparated monocytes. In contrast, CD64- monocytes are characterized by high expression of major histocompatibility complex (MHC) class I antigens (HLA-A, -B, -C) and MHC class II antigens (HLA-DR, -DP, -DQ), and low expression of the monocyte-specific marker CD14 which is found on nearly all CD64+ monocytes. However, 75% of the CD64- cells were found to be esterase-positive, and 85% were positive for the the CD64- cells were found to be esterase-positive, and 85% were positive for the monocyte/macrophage-specific intracellular antigen CD68. Furthermore, CD64- monocytes show significantly higher expression of CD45RA and Fc gamma receptor III (CD16) than CD64+ monocytes, but lack the natural killer cell markers CD56 and CD57. Functional studies showed that cells of the minor CD64- monocyte subset have a higher accessory cell capacity in antigen-driven T cell activation than CD64+ monocytes. CD64- monocytes pretreated with PPD (purified protein derivative of tuberculin) induced up to tentimes more interferon-gamma and also higher proliferation in responding autologous T cells than PPD-pretreated CD64+ monocytes. Similar results were obtained for T cells in mixed leukocyte reaction. Interferon-gamma release and proliferation of allogeneic lymphocytes were consistently higher in the presence of irradiated CD64- monocytes than of irradiated CD64+ monocytes. Furthermore, when CD64- and CD64+ monocytes were stimulated with Newcastle disease virus, we measured an up to 67-fold higher interferon-alpha release from CD64- than from CD64+ monocytes, indicating a higher anti-viral capacity of this subset. CD64- monocytes showed lower activity in the phagocytosis of unopsonized particles and also lower zymosan- or latex-induced chemiluminescence than CD64+ monocytes. These findings indicate that CD64- monocytes, although comprising only less than 10% of all peripheral blood monocytes, represent a monocyte subpopulation efficiently interacting in vitro with T cells and, additionally, are the major source of interferon-alpha.

The human neutrophil-activating peptide 2 (NAP-2) belongs to the so-called beta-thromboglobulin/interleukin 8-family of chemotactic and reparative host defense cytokines. NAP-2 represents one of several N-terminally truncated cleavage products that originate from platelet-derived precursor molecules through proteolytic processing. Among these homologous isoforms that are comprised as beta-thromboglobulin antigen (beta-TG Ag), NAP-2 is recognized as the major component, having the highest potential for the activation of polymorphonuclear neutrophils (PMN). We now present evidence that there exists a second molecular form of NAP-2 with even higher biological activity. This novel isoform was detected in concentrates of culture supernatants from peripheral blood mononuclear cells, and could be separated from authentic NAP-2 by several steps of column chromatography. It had an N-terminus identical to that of NAP-2 but was biochemically different as indicated by its slightly lower molecular weight and a higher isoelectric point. To examine our hypothesis that the polypeptide represented a C-terminally truncated variant of NAP-2, we prepared synthetic peptides that were used for the induction and characterization of two rabbit antibody fractions, directed against different and defined epitopes within the C-terminal alpha-helix of the NAP-2 molecule. Comparison of reactivity patterns of these antibodies in Western blots as well as in a NAP-2 biological assay (PMN degranulation assay) confirmed that the variant NAP-2 was truncated at its C-terminus by at least one and by maximally three residues. The specific activity of the truncated polypeptide was estimated to be about four-fold higher than that of authentic NAP-2, as determined in the PMN degranulation assay. Thus, proteolytic modification at the C-terminus appears to play a role in the regulation of NAP-2-biological activity.

Intragraft production of tumor necrosis factor-alpha (TNF-alpha) and interleukin-1-beta (IL-1-beta) was determined in rejecting human liver grafts during acute rejection and in chronic graft dysfunction. The localization of cytokine-producing cells was then correlated with the distribution of monocytes and macrophages as their main producers, as well as with effector functions such as endothelial cell activation. In selected patients collateral TNF-alpha plasma levels were measured. In normal liver and biopsies taken during an uncomplicated course, few TNF-alpha and even fewer IL-1-beta positive macrophages were found. During acute rejection episodes of all degrees of severity liver grafts were infiltrated by large numbers of TNF-alpha-positive monocytes, and concomitant TNF-alpha plasma levels were elevated compared with uncomplicated controls. In marked contrast IL-1-beta production by macrophages and vascular and sinus endothelial cells was restricted to the most severe, irreversible rejection episodes. The localization of cytokine-positive cells coincided with areas of maximum induction of ICAM-1 and von Willebrand Factor. In chronic graft dysfunction increased numbers of mature macrophages were found. A large proportion of these were positive for TNF-alpha as well as IL-1-beta. Distinct from acute rejection episodes, however, parallel TNF-alpha plasma levels were not elevated, suggesting cytokine storage rather than secretion. The present results indicate an important local role of TNF-alpha and IL-1-beta in the early phase of the rejection process. They presumably activate endothelial cells to upregulate the expression of adhesion molecules, thereby facilitating mononuclear cell adhesion and extravasation. Therefore, specific inactivation of cytokines or of their actions may prove to be a powerful tool in the prevention and treatment of allograft rejection in the future.

The effects of synthetic alkyl ((alkyl 6-deoxy-a-D-gluco-heptopyranosyluronate) 6-deoxy-a-D-gluco-heptopyranoside) uronates, a novel type of mirror pseudo cord factor, on the in vitro modulation of interleukin-6 production and T-cell proliferation in human peripheral blood mononuclear cells, were investigated. Synthetic mirror pseudo cord factors with alkyl chains ranging from C16 to C18 have very weak interleukin-6-inducing capacities and lack mitogenic activities for T-cell proliferation. However, they could inhibit IL-6 release induced by sonicated Bacillus Calmette-Guérin (S-BCG), bacterial endotoxin, and phytohaemagglutinin in a dose-dependent manner. Inhibition was observed not only with mononuclear cells but also with purified monocytes. Furthermore, these synthetic compounds could suppress T-lymphocyte proliferation stimulated by sonicated Mycobacterium tuberculosis H37Rv (S-H37Rv) antigens, S-BCG antigens, as well as by recombinant 65 kDa mycobacterial heat-shock protein. In contrast, these compounds failed to inhibit the phytohaemagglutinin-induced T-cell proliferation. We conclude that the inhibition of cytokine release and T-cell proliferation by synthetic mirror pseudo cord factors was due to direct blocking of the function and/or activity of monocytes or antigen-presenting cells.

Endotoxin (lipopolysaccharide, LPS) induces the production of mediators of inflammation, which exerts pathophysiological effects such as fever or shock in mammals. In the present study we have investigated the modulation of LPS by the synthetic non-active tetraacylated precursor Ia of lipid A (compound 406) in the induction of tumor necrosis factor (TNF), interleukin 1 (IL-1) and interleukin 6 (IL-6) in human peripheral blood mononuclear cells (PBMC) and in human peripheral blood monocytes (PBMo). PBMC stimulated with LPS released TNF in a concentration dependent manner. Release of biologically active TNF, IL-1 and IL-6 was first detectable 4 h after LPS stimulation. Compound 406 alone in all concentrations tested did not induce TNF, IL-1 or IL-6 release, intracellular TNF or IL-1 beta, or mRNA for TNF or IL-1. Added to PBMC 1 h before LPS compound 406 enhanced or suppressed TNF release and suppressed IL-1 and IL-6 release depending on the ratio of concentrations between stimulator (LPS) and modulator (compound 406). In contrast to LPS stimulation alone TNF, IL-1 and IL-6 release in presence of compound 406 was delayed and first detectable after 6 to 8 h. Compound 406 was able to suppress LPS-induced intracellular TNF and IL-1 beta in PBMC. Added to PBMo 1 h before LPS it totally inhibited the production of mRNA for TNF and IL-1. When added to PBMC 1 h after LPS, TNF release was suppressed in a concentration-dependent way and release of biologically active TNF, IL-1 and IL-6 could again be detected for the first time after 4 h. Compound 406 was not able to inhibit phorbol 12-myristate 13-acetate (PMA)-induced TNF and IL-1 release in PBMo which suggests that its modulating effect is LPS-specific. This study provides evidence that the modulating effect of compound 406 on the LPS induction of TNF, IL-, 1 and IL-6 could be due to competitive binding.

The identification of chemokines in blood platelets has strengthened our view of these cells as participants in immune host defense. Platelet chemokines representing prestored and rapidly releasable proteins may play a major role as first-line inflammatory mediators. This is evident from their capability to recruit early inflammatory cells such as neutrophil granulocytes and monocytes and even to exhibit direct antimicrobial activity. However, insight is growing that platelet chemokines may be also long-term regulators, e.g., by activating T lymphocytes, by modulating the formation of endothelium and even thrombocytopoiesis itself. This review deals with the individual and cooperative functionality of platelet chemokines, as well as their potential as a basis for therapeutic intervention in the pathology of inflammation, infection, allergy and tumors. Within this context, therapeutic strategies based on the use of antibodies, modified chemokines, chemokine-binding proteins and chemokine receptor antagonists as well as first clinical studies will be addressed.

The significance of endotoxins in bacterial infection and their role as bacterial surface antigens (O antigens) have stimulated investigations into their chemical nature and the mechanisms of their biologic action during the last few decades. This article summarizes some of the recent results and emphasizes structure-activity relationships.

The effect of two synthetic lipid A partial structures, compound 406 (or LA-14-PP, identical in structure to the lipid A precursor, known as Ia or IVa) and compound 401 (lipid X), on the in vitro modulation of endotoxin (lipopolysaccharide)-induced interleukin-6 production by human blood mononuclear cells was investigated. Lipopolysaccharide of Salmonella abortus equi and synthetic Escherichia coli-type lipid A (compound 506, or LA-15-PP) had potent interleukin-6-inducing capacities. The maximum release of interleukin-6 was found after stimulation with 1 to 10 ng of lipopolysaccharide or 10 to 100 ng of synthetic E. coli-type lipid A per ml. Both synthetic lipid A partial structures (compounds 406 and 401) failed to induce interleukin-6 release. However, they inhibited lipopolysaccharide- or lipid A-induced interleukin-6 production in a dose-dependent manner. Inhibition was found not only in mononuclear cells but also in purified monocytes and was not due to a shift in the kinetics of cytokine production. Suppression was manifested in the early stage of interleukin-6 production. Inhibition was also found in the presence of recombinant gamma interferon, indicating that compound 406 and recombinant gamma interferon act in different, independent pathways. Our data, therefore, indicate that the inhibition of interleukin-6 production by lipid A partial structures may help elucidate the mechanism of interaction of the lipid A component of lipopolysaccharide with immune cells in the inflammatory reaction during gram-negative infection.